a. Field of the Invention
The invention relates to a zooming adjustment mechanism and a projection lens module having the zooming adjustment mechanism.
b. Description of the Related Art
Taiwan patent no. TWM339013 discloses a conventional turning mechanism used for projector. Referring to FIG. 1, a zoom projection lens 210 is mounted on a holder 200, and a turning mechanism 100 is used to turn a zoom bar 212 of the zoom projection lens 210. The turning mechanism 100 includes a fixed element 110 and a movable element 130. The fixed element 110 is fastened to the holder 200 and has a pair of sliding tracks 112. The movable element 130 has a pair of sliding edges 132 and a pair of hooks 134. The movable element 130 is clipped to the sliding tracks 112 through the hooks 134, and the sliding edges 132 lean against the sliding tracks 112 to allow the movable element 130 to slide around an optical axis R of the zoom projection lens 210 and relative to the fixed element 110 so as to turn the zoom bar 212. However, though the turning mechanism 100 allows for an adjustment to the focal length of the zoom projection lens 210, such design fails to provide smooth feel when a user pokes the movable element 130 to adjust the focal length of the zoom projection lens 210. In an alternate conventional design, a Teflon sheet is adhered to a surface of the holder 200 by a backing adhesive, and the movable element 130 slides on the Teflon sheet to provide smooth feel during a poke operation. However, as time goes on, the Teflon sheet is gradually worn out to fail to provide smooth feel. Besides, the backing adhesive is liable to peel off as a result of high usage frequency.
Taiwan patent publication no. TW200938937 discloses a zooming adjustment mechanism for a projector. The zooming adjustment mechanism has an adjusting ring, a transmission gear and a driving ring engaging with each other to adjust the focal length of a lens module in a lens barrel. Further, Taiwan patent no. TWI279639 discloses a magnification-adjusting mechanism to adjust the magnification of a projection lens. The magnification-adjusting mechanism is installed outside and around a lens barrel and includes an adjusting ring and a roller. The adjusting ring is installed outside the lens barrel in a rotatable manner relative to the lens barrel, and a slot is formed on the adjusting ring. The roller is installed between the adjusting ring and the lens barrel.